When a vehicle collision occurs with the driver/passenger seated, the driver's/passenger's waist moves forward along the seating portion of the seat under a forward inertia and the driver's/passenger's upper body tends to fall forward about his or her waist acting as fulcrum.
When an air bag arranged forwardly of the driver/passenger receives and stops the driver's/passenger's upper body in such a condition, the driver's/passenger's upper body is positioned closer to the air bag by an amount corresponding to the forward movement of the driver's/passenger's waist along the seating portion of the seat. Thus, the driver's/passenger's upper body would reach the air bag sooner as it starts falling forward. In other words, the stroke of forward fall of the driver's/passenger's upper body is reduced by the amount of forward movement of the driver's/passenger's waist along the seating portion of the seat, to absorb the shock within the reduced stroke of forward fall of the driver's/passenger's upper body. This is undesirable in terms of shock absorption for the driver/passenger by the air bag.
Hence, it is required that the air bag should receive the driver's/passenger's upper body without reducing the stroke of forward fall of the driver's/passenger's upper body by restraining the driver's/passenger's waist from moving forward along the seating portion of the seat.
In this case, an example is shown in Japanese Patent Application “Kokai” No. 11-139233 in which a lower air bag is arranged inside a lower portion of an instrument panel. By inflating the lower air bag, part of the instrument panel is separated and moved toward the seat positioned rearward. As a result, the separated part of the instrument panel receives and stops the driver's/passenger's knee regions to restrain the driver's/passenger's waist from moving forward along the seating portion of the seat.
Where the part of the instrument panel is separated and moved toward the seat positioned rearward as disclosed in the above-noted conventional art, in addition to the aspect of restraining the driver's/passenger's waist from moving forward along the seating portion of the seat, it is an important consideration to control the impact acting on the driver's/passenger's knee regions when the part of the instrument panel receives and stops the driver's/passenger's knee regions.
In this case, it is expected that the part of the instrument panel should be deformed when receiving and stopping the driver's/passenger's knee regions thereby to absorb the impact exerted on the driver's/passenger's knee regions.
However, since the instrument panel of the prior art is made of synthetic resin, part of the instrument panel is sometimes bent linearly (see FIG. 6 of Japanese Patent Application “Kokai” No. 11-139233 as noted above) when it receives the driver's/passenger's knee regions. This leaves room for improvement in terms of controlling the impact exerted on the driver's/passenger's knee regions.
Therefore, the object of the present invention is to provide an instrument panel construction for a vehicle capable of receiving the driver's/passenger's knee regions when a great impact acts on the vehicle and restraining the driver's/passenger's waist from moving forward along the seating portion of the seat while controlling the impact exerted on the driver's/passenger's knee regions.